This report describes the results of a meta-analysis of a number of small-scale studies into the effects of changed road markings on the speed and lateral position of motor vehicles. It was examined whether predictions can be made about the general effects of altered road markings. Several kinds of alterations were studied, such as applying an edge line to a previously unmarked road or to a road that was already marked with a centre line. Firstly, the authors studied the general effects of these different kinds of road markings. Next, the study focused on those alterations that correspond to replacing the current road markings in the Netherlands by the markings proposed for the three sustainably safe road categories (through roads, distributor roads and access roads). As far as the general effects of altered road markings are concerned, the results of this meta-analysis showed that adding an edge line or a centre line to a road that was previously unmarked leads to an increase in the speed driven and a shift of the lateral position towards the edge of the road. The actual effects on road safety are not known, since accident data were not included in the studies on which the meta-analysis was based. With respect to the alteration of road markings as part of the implementation of a sustainably-safe traffic system, the meta-analysis shows that up till now, very little research has been done on the effects of these alterations on road user behaviour. The only sustainably-safe road type for which enough data was available, was the access road. The results of the experiments that have studied alterations in road markings that were relevant for this type of road, point into the direction of a small decrease (-2 kilometres per hour) of the mean speed driven.
Samenvatting